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Stormwater Impaired Waters

As watersheds become more developed, the effects of stormwater runoff are being increasingly seen in our waters. Instead of infiltrating naturally into the soil, water quickly runs off of roofs and paved surfaces, picking up pollution and carrying it to waterways. Increased flows during storm events destabilize stream channels and put biological communities in jeopardy. ANR recognizes the importance of managing the quantity and quality of stormwater runoff, especially within Vermont’s stormwater impaired waters.

Seventeen of Vermont’s waters are listed as “impaired,” primarily due to urban stormwater runoff. These waters fail to meet the Vermont Water Quality Standards based primarily on biological monitoring data.

Once a water is listed as impaired, it is scheduled for the development of a Total Maximum Daily Load (TMDL). A TMDL is an EPA approved document that attempts to limit and allocate discharge loads among the various dischargers to impaired waters in order to assure attainment with water quality standards. The Department has issued EPA-approved hydrologic TMDLs for the twelve urban watersheds as listed below. For more information on the development of the TMDLs, see the Stormwater TMDL page.

During 2008, VT DEC held meetings with a group of stakeholders known as the Stormwater Advisory Group or SWAG to discuss issues and strategies associated with implementing the stormwater TMDLs. The culmination of this effort was the creation of an overall framework for remediation of the stormwater-impaired waters. Information from the meetings and final report are available on the SWAG page.

Remediation of the twelve urban stormwater-impaired waters has commenced through a combination of permits issued pursuant to Vermont’s federally delegated National Pollutant Discharge Elimination System (NPDES) permitting program. These permits include a reissued and enhanced NDPES permit for small municipal separate storm sewer systems (MS4s), which was issued on December 5, 2012. Under the reissued permit, MS4 permittees must develop a Flow Restoration Plan for any stormwater impaired water to which they discharge. A computer-based best management practice decision support system (BMPDSS) was developed by TetraTech and is being used by VTDEC to help affected MS4 communities to identify different BMP options and associated costs.

Five mountain watersheds are listed as impaired primarily due to stormwater runoff on the 2016 EPA-approved 303d List of Impaired Waters (Part A). The mountain watersheds differ substantially from the remaining urbanized “lowland” watersheds in terms of density of development, geographic position, hydrology, impairment source, and land ownership. Based on these factors, the Department has concluded that use of the so-called “4b alternative,” a non-TMDL based alternative pollution control strategy, is the best implementation strategy. The Department is working with responsible parties developing watershed-specific WQRPs for the impaired mountain watersheds.

Currently, expired permits in the impaired waters are not able to be renewed under a General Permit unless they have been residually designated. Until a plan has been established to implement the TMDLs, affected watersheds will have to comply with the "net zero" pollution standard described in the 9/27/2004 letter describing New Legislation relating to Stormwater Discharges. To apply for an Individual Discharge permit (INDS) for a new discharge to a stormwater-impaired water, or to renew an INDS permit, see the stormwater application forms and worksheets. For questions regarding the permitting of a site in an impaired watershed, permittees should contact the permit reviewer for their district.